As the globe continues to warm, layers of snow and permafrost are beginning to melt. Suspended in this melting snow and ice are a host of bacteria and viruses that have been trapped for thousands, if not millions of years.
In a 2005 study, NASA scientists were able to revive bacteria that had been frozen in an Alaskan pond for nearly 32,000 years. Similarly, a research team in 2014 was able to revive two viruses that were trapped in the Siberian permafrost for 30,000 years. Both of these discoveries serve as a proof of concept that viruses and bacteria, trapped in ice and snow, can be revived after lengthy periods of time and still maintain their ability to infect their hosts.
Implications of such findings suggest that there is at least a possibility that as the earth warms, pockets of ice that previously trapped pathogens will melt. It is unknown exactly how the pathogens that are released will interact with the biological life of today. However, there has been evidence that demonstrates warming environments have caused melted ice to release frozen pathogens that infected reindeer and sea lions.